In the supplying of any type of web materials from finite length supplies such as in roll form, including papers, films, woven and non-woven fabrics, adhesive tapes or the like, to be converted or otherwise applied to another material in a production line setting, it is desirable to minimize production line downtime caused by changing from one supply roll to another. One way of minimizing downtime is to use larger capacity rolls. A way of eliminating downtime is to provide for a changeover without interrupting the continuous material supply.
Under such continuous demand situations, it is known to incorporate a splicing mechanism into the web material supply to effect a roll changeover from a depleted roll to a new roll while the demand continues; that is, without stopping the supply of web material to the conversion or application systems. Typically, a new supply roll will be loaded onto the splicing mechanism in a ready position so that upon depletion of the current supply roll (or upon the expectation of such event), a leading edge of the new roll will be relatively moved to adhere or be otherwise connected to the remaining web material of the depleted roll. Upon such connection, the new roll will provide the currently demanded supply, and yet another roll can be readied for the next changeover.
Splicing mechanisms suitable for such use can be classified as either of the type that splices the new web material to the currently demanded web material while it is in motion, hereinafter referred to as an "on the fly" splicing mechanism, or of the type that splices the new web to the demanded web while it is temporarily stopped, hereinafter referred to as a "zero speed" splicing mechanism.
On the fly mechanisms may bring the web material of the new roll up to the demand speed before splicing or may let the demanded web material pick up the new web material from a lower speed or a stationary position. Zero speed splicing mechanisms must provide for a temporary supply of web material downstream from the splicing mechanism through which the demanded web material runs so that the web material can be temporarily stopped within the splicing mechanism during the splice. The capacity of the temporary supply must be sufficient to provide for the continuous demand for the time period over which the splice takes place. Usually, such capacity is provided by an accumulator comprising a loop or series of loops, hereinafter referred to as a festoon, which can be decreased in size during the continued demand while the web material is stopped at the splicing mechanism. The size of the festoon is then gradually increased to full capacity after the splice is completed. An obvious advantage of the on the fly splicing mechanisms is that they do not require the provision of a festoon after the splice mechanism. However, with the on the fly mechanisms, it is essential that the splice be precisely controlled so as to reliably effect such a connection of a new web to a moving web.
Examples of known apparatuses for splicing a web to another web, and in particular from a replacement web to a moving web are disclosed in U.S. Pat. Nos. 4,172,564 to Romagnoli, 4,264,401 to Ganz, 4,848,691 to Muto et al., 5,033,688 to Georgitsis et al., and 5,064,488 to Dickey. Each of these, however, deals with the situation of splicing one web to a moving web under a continuous and constant demand for the web material.
Although such splicing techniques for splicing one roll of a web material to another roll of web material, including the splicing of one adhesive tape to another adhesive tape, are known under continuous demand situations, such splicing techniques have heretofore not been utilized in an intermittent demand situation. Under a continuous demand situation, the tension within the web remains substantially constant over the use of the entire roll by virtue of the even demand. Thus, splicing can be effectively controlled. To the contrary, an intermittant demand of the web material from the supply roll causes the tension within the web to fluctuate. Thus, in addition to supplying the web material, the tension thereof should be controlled to provide a substantially even tension throughout each demand cycle to minimize web feeding problems and failures.
Moreover, when dealing with the supplying of adhesive tape from a supply roll to a tape applicator machine, the stripping tension, that is the tensile force that is required to pull the adhesive tape from the roll, is very often significantly higher than the desired tension of the tape as it is supplied to the applicator machine. Thus, it may also be desirable to perform a reduction in the tape tension after it is stripped from its roll and before it is fed to the applicator machine. In the case of an intermittent demand type tape applicator machine, both tension reduction and tension evening may be necessary. Thus, any attempted splicing must also be accomplished within these difficult to control tension requirements.
Tape applicator machines are used in many ways for applying continuous lengths of tape or discrete lengths of tape to a variety of objects that are moved relative to the tape applicator. Of such tape applicator machines, one specific type is box sealing machines, also known as case sealers, which apply a length of tape to a box or carton to seal the box by taping the top flaps together.
Such box sealing machines may apply a length of tape in a configuration known as a C-clip which is applied with a portion of the tape to a front vertical portion of the box, over the top to seal the top flaps together, and then down a portion of the rear vertical wall. Otherwise L-clips of tape are sometimes provided at either the front or rear edges of the box or both, or a length of tape is adhered only to the top surface to connect the flaps. In any case, these machines have in common that the tape is demanded intermittently. In other words, tape is demanded from its supply as a length of tape is applied to one of such boxes or cartons by a tape applicator, and then the tape demand is stopped for a moment until the next box is positioned relative to the tape applicator for the next application. Moreover, typical intermittant tape demand of a box sealing machine, hereinafter referred to as indexing demand, can be characterized generally as a square wave representing an immediate demand upon the start of application of tape to a box up to the level (rate) of demand that is then substantially constant during the application of the tape length to the box until demand is ceased immediately upon the cutting of the length of tape from its supply roll.
Such intermittent applications may occur indefinitely as the boxes or cartons are fed along a continuous packaging line. However, such applicator machines have in the past been provided with only a limited supply of such adhesive tape. Thus, at some regular interval, the packaging line must be stopped so that a new roll of tape can be loaded into the applicator machine. Moreover, with the increasingly high demands for such packaging lines, which demand as much as about 200 feet of tape per minute (61 meters per minute), the interval may be too short requiring even more down time of the packaging line.
One attempt at minimizing the down time of production packaging lines, particularly those which run at relatively high speeds, is the designing and making of larger rolls of tapes. Moreover, specially wound tape rolls have been developed which provide as much as six times the amount of tape found in a typical tape roll. Such specially wound tape rolls are available from Minnesota Mining and Manufacturing Company of St. Paul, Minn. under the trademark Opta-pak. Although these rolls effectively minimize down time of a packaging line, they still must, by the virtue of the fact that they are a definite length, require some down time of the production line in order to change to a new roll.
The intermittent demand of such box sealing machines and similar applicators require that the tape tension be effectively controlled during the intermittent demand for smooth unwinding of the tape from the roll. Moreover, in many cases, a relatively high tension in the order of 3.5 lbs is necessary to strip the tape from its roll. On the other hand, the application of the tape to the objects should preferably be done at a relatively low tension of below 1 lb. Thus, it is important to effectively strip the tape from the roll at the required high tension while applying the tape to the objects at the relatively low tension and doing so smoothly under the indexing demand, described above, so as to minimize tape jams, failures or damage to boxes or cartons.
The present invention deals with the supplying of an uninterrupted supply of tape to such an intermittent demand tape applicator machine. Moreover, the present invention utilizes a tape splicing technique for providing the continuous length of tape and does so while accommodating the aforementioned tension requirements.
Other apparatuses have been developed for application of a discrete length of a web material, such as a deadening strip, to a portion of the continuous length of adhesive tape supplied in roll form and as thereafter applied on intermittent demand. Such devices have been used to provide tabs or handle portions, or the like to the length of tape as applied to a box or carton. Examples of tape handle producing and applying apparatuses are described in U.S. Pat. Nos. 4,906,319 to Fiorani and 5,145,108 to Pinckney et al. Moreover, an example of a device for providing tabs to the adhesive tape to facilitate removal of the tape from boxes is described in commonly owned U.S. patent application Ser. No. 08/002,194. None of these devices, however, provide a changeover operation from one roll to another. Such changeover operation is a critical part of a continuous tape supply system which requires that a plurality of tape rolls must be accommodated and controlled under the above-noted tensioning requirements.